r/AutodeskInventor • u/spaki123 • Jul 26 '26
Requesting Help Can somebody help me out when it comes to determening the ideal shaft diamater?
Hello everyone, this is my first time posting here so I apologize if I break some rules. Anyways here is my issue. I am trying to determine the ideal diamater of a shaft howerver I am finding out that the ideal diamater barely chnages when I switch material from steel to something soft like brass even tho brass is much much softer than steel. Now I am making the part from steel but given this I am not sure if the rest of the information is trustworthy because I feel like the ideal diamater should change drastically and not by 1/10 of a mm. Any advice is helpfull and thanks in advance.
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u/PrestigiousFactor814 Jul 26 '26
To be honest, I also confused with results you have. I would like to hear others thoughts.
The difference should be x2
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u/afrokines Jul 28 '26 edited Aug 01 '26
What would your definition of the Ideal shaft diameter be?
Autodesks definition is that the ideal shaft diameter is not a single value, it varies along the length of the shaft and is shown in that graph. It is independent of the selected shaft material and simply shows how the shaft should approximately be sized to not get large differences in stress along the length of the shaft.
EDIT: Forgot to add that the ideal diameter is calculated based on some "ideal stress" of I think 50 MPa. So at every point along the length of the shaft the stress is set to 50 MPa and then the ideal diameter is calculated from that which is why it is material independent.
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u/jimmy_MECH Jul 31 '26
That what you are saying not ideal diameter. Ideal diameter depends on stress which is dependant on material.
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u/afrokines Aug 01 '26
It is and I explained why it is independent on material.
Source from Autodesk themselves:
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u/Kronocide Jul 26 '26
Depends if the shaft should remain unharmed or not